Conventional plating of plastics as pointed out in U.S. Pat. No. 3,556,955, conditions the plastic in a strong oxidizing solution, e.g. aqueous sulfuric acid-chromic acid. The plastic is next sensitized in a solution of a reducing agent such as stannous chloride and then activated by immersion in a noble metal salt solution before passing the plastic to an electroless plating bath.
This general method with the prior art polymers suffers from numerous disadvantages among which are the complexities of the process and the hazards and disposal problems with the chromic acid bath as well as lesser physical properties of the plated polymers. Various methods of overcoming some of these problems are proposed in U.S. Pat. Nos. 3,556,955 and 3,701,675. Polymers with acid groups or treated to have acid groups are neutralized with ammonia, alkali solutions or ethylenimine according to U.S. Pat. Nos. 3,567,488; 3,567,489 and 3,607,350. The polymers are then treated with a noble metal salt solution before being plated. U.S. Pat. No. 3,222,218 is similar to Czech Pat. No. 100,373 in that ion exchange groups on a polymer are treated with a noble metal salt and after ion exchange are reduced and then plated. Because plastic materials are non-conductive and inert to metals, adhesion of the metal plate to the plastic is a basic problem in the metallization of plastics.